Robust technique for computation of scattering and absorption of light by array of nanowires on layered substrate

In this study a robust semi-analytical technique based on the transition matrix approach is introduced for computation of scattering and absorption of light by periodic and aperiodic arrays of nanowires located on layered substrates. The formulation is developed for obliquely incident plane waves and then by means of suitable plane-wave decomposition, it is extended to Gaussian beams. The substrate contribution is taken into account through spectral reflection and transmission coefficients, which leads to computation of 2D Sommerfeld-type integrals. The major advantage of the proposed method is the rapid calculation in characterizing various types of large arrays (gratings) of nanowires on layered substrates. The analysis is applied to the grating of nanowires separated from a thick metallic film by a thin dielectric spacer. We investigate the influence of spacer-layer thickness and periodicity of arrays on the resonant behavior of structure. The study shows how, by engineering these parameters, the scattering properties can be tailored for specific applications. We demonstrate full-visible-range resonant light scattering by adjusting these parameters, which gives us control over color perception. Furthermore, in order to demonstrate the efficiency and capability of our model, we integrate the technique with genetic algorithm in an optimization procedure to design graded pattern meta-surfaces for focusing light and beam steering. The method will be of great advantage for designing various optical devices managed by nanowires, for both scattering and absorption. (C) 2015 Optical Society of America